1. Technical Field
The present invention relates to a disk brake apparatus, particularly to a disk brake apparatus comprising a piston for hydraulically pressing friction pads, an adjuster for automatically adjusting the gap between the pads and a disk rotor, and a parking brake for pushing the piston through the adjuster by a ball ramp type thrust conversion mechanism.
2. Background Art
A disk brake apparatus with a parking brake, comprising a hydraulic actuating mechanism operated by a brake pedal, and a mechanical actuating mechanism configured to be pulled by a hand lever or a foot pedal is known as one of disk brake apparatuses for use in a four-wheel vehicle or the like. In general, a piston that constitutes a part of the hydraulic actuating mechanism is placed on the distal end opening side of a cylinder hole provided in the caliper body, and an adjuster having an adjuster nut and an adjuster bolt is placed on the back side of the piston in such a disk brake apparatus with a parking brake. Furthermore, a thrust conversion mechanism that constitutes a part of the mechanical actuating mechanism is placed on the bottom side of the cylinder hole.
Conventionally, a ball ramp type thrust conversion mechanism has been widely used as the thrust conversion mechanism. In the ball ramp type thrust conversion mechanism, a fixed side cam plate and a drive side cam plate, both of which have their respective ramp grooves formed therein for accommodating cam bearings, are placed opposite to each other. By turning the drive side cam plate through the parking brake operation, a thrust for moving the piston to the disk rotor side is generated by the cam action of the ramp grooves and the cam bearings. Then, the thrust pushes the piston to the disk rotor side through the adjuster and presses the friction pads to the disk rotor so that the braking force is generated.
Furthermore, in some cases, the thrust conversion mechanism, the adjuster having a thrust transmitting plate, and a cam spring for pushing the thrust transmitting plate toward the thrust conversion mechanism are accommodated in a generally cylinder-shaped housing, and engaging protrusions formed on the outer circumference of the thrust transmitting plate engage in the engaging apertures formed on the circumferential wall of the housing in an attempt to prevent the rotation of the thrust transmitting plate (see Japanese Patent No. 2739879 and Japanese Unexamined Patent Publication No. 2000-136838). Furthermore, in some cases, portions of the circumferential wall of the housing are partially cut and bent outwardly to form plural locking parts, and a C-shaped ring is attached to the cylinder hole opening sides of the locking parts. Then, the housing is mounted to the housing mounting portion of the cylinder hole through the C-shaped ring (see Japanese Patent No. 2739879).